1. Field of the Invention:
This invention relates to sealing members, especially for use as packings to seal and block the space between the inner wall of a hollow cylindrical pipe and the outer wall of a pipe of smaller diameter located coaxially within it. The invention relates particularly to oil and other wells of the common type in which the well casing, extending from the well head down to the oil reservoir formation, is a long cylindrical pipe in the form of a string of many pipe sections screwed together. Within the casing is a second pipe string of similar length but of smaller diameter which is generally known as tubing. The tubing services to conduct the fluids produced by the well to the well head but may also serve to conduct fluids being injected into the well. To prevent these fluids from entering into the annular space between the tubing and the casing a device called a packer member is commonly employed. The packer typically comprises a hollow cylindrical member inserted into or mounted upon the tubing by a coupling, and supporting a packing ring of a flexible elastomeric material, which is compressed against the inner wall of the casing to form a tight joint.
2. Description of the Prior Art:
In some applications a well may be used to inject steam or hot water into an oil-bearing formation in order to increase the fluidity of the oil and cause it to flow to neighboring wells, where it is produced. Alternatively, the steam may be injected for a short period and oil subsequently produced through the same well. The steam is injected down the tubing and a packer may be used to prevent the steam from entering the annulus between the tubing and the casing. However, typical elastomeric packing rings are not suitable for use with steam at high temperatures and pressures.